The present invention relates to a computer-based process controller, and more particularly to a computer-based process controller including graphical display of selected process attributes.
Processing plants typically include a series of operations in which liquid, gas and solid materials are transported, heated, mixed, chemically treated, cooled, pressurized or otherwise processed. Each of the operations in a processing plant are monitored and controlled to ensure that each is performed according to some predetermined specification or criteria. The monitoring and control typically requires instrumentation including sensors for various process conditions, transmitters for transmitting the sensed data to a computer-based controller, a computer-based controller that receives the transmitted sensed data and that takes appropriate control action based on the sensed data, and controlled elements within the process such as valves, pumps, conveyors, heating or cooling elements, alarms, and the like, which are connected to and controlled by the process controller in order to maintain the sensed process conditions within predetermined desired limits to thereby control the operation of interest.
Typical processing plants, such as oil refineries, petrochemical plants, food processing plants, or drug processing plants, may include operations that have tens or hundreds of such so-called "loops", each of which may contain any type of sensor and transmitter, the computer-based controller, and any type of controlled element. Such loop-based operations are typically represented by loop drawings or loop sheets which graphically illustrate the loop or loops of the operation of interest.
With the advent of Computer-Aided Design (CAD) programs, loop drawings are created and stored in a computer memory, and are displayed on a display screen, thus simplifying the creation and maintenance of loop sheets. With such CAD programs, creation of the loop sheets was accomplished by an operator instructing the computer, using a digitizer or mouse, to place and connect graphical representations of the components of the operation on the display screen of the computer-based controller.
Such CAD programs and computer-based process controllers also facilitated the maintenance of historical data related to the operation under control. Such data historians operate much like flight recorders on aircraft, and serve to record a history of the states and other attributes of all control elements in an operation. The maintenance of such historical data has proven particularly critical when the operation being controlled relates to the manufacture of foods and/or drugs.
Typical data historians simply keep track of all attributes of all components of the operation under control, and maintain the data history in a large history data base. Then, when review of the history data base is desired, for example, after the detection of a process upset or other error, the history data base is output in the form of a spread sheet, thus permitting a system operator to analyze the historical data to determine the cause of the upset or error. During such an analysis, an operator reviews the spread sheet of historical data, in combination with a loop sheet drawing, to render conclusions, for example, as to the cause of the upset or other error. Such analyses have proven difficult because large portions of the history data base may not be relevant to the particular loop or process upset under consideration. In addition, correlating the data history with a loop sheet of interest to determine the history of a particular component of the operation of interest, often proves time consuming and occasionally results in errors.
There is therefore a need to provide an easier method to correlate data history with individual components in a computer-based process controller.